Add regex validation pattern in schema version property

src/probeinterface/schema/probe.json.schema

@@ -1,5 +1,7 @@
 {
   "$schema": "http://json-schema.org/draft-07/schema#",
+  "$id": "https://probeinterface.readthedocs.io/schema/probe.json.schema",
+  "$comment": "Validates probeinterface specification versions matching the 'version' property pattern (currently 0.3.x). The pattern is bumped only when the schema changes incompatibly. See https://probeinterface.readthedocs.io",
   "type": "object",
   "properties": {
     "specification": {
@@ -8,7 +10,8 @@
     },
     "version": {
       "type": "string",
-      "pattern": "^\\d+\\.\\d+\\.\\d+$"
+      "$comment": "Range of specification versions this schema validates. Bump when the schema changes incompatibly.",
+      "pattern": "^0\\.3\\.\\d+$"
     },
     "probes": {
       "type": "array",

tests/test_schema.py

@@ -0,0 +1,29 @@
+import re
+
+from probeinterface import __version__
+from probeinterface.testing import schema
+
+
+def test_schema_is_annotated():
+    """The schema must carry the annotations documenting what it validates."""
+    assert schema.get("$schema"), "The schema must declare the JSON Schema draft it uses ('$schema')."
+    assert "specification versions" in schema.get(
+        "$comment", ""
+    ), "The schema '$comment' must document which specification versions it validates."
+
+
+def test_package_version_is_compatible_with_schema():
+    """
+    The current package (specification) version must match the compatibility pattern
+    declared by the schema's 'version' property.
+
+    The schema rarely changes, so it stays compatible across many releases. When a
+    release introduces an incompatible schema change, bump the 'version' pattern in
+    ``src/probeinterface/schema/probe.json.schema`` (e.g. to allow ``1.x.y``).
+    """
+    pattern = schema["properties"]["version"]["pattern"]
+    assert re.fullmatch(pattern, __version__), (
+        f"The package version ({__version__}) does not match the schema's declared "
+        f"compatibility pattern ({pattern}). Either this is an incompatible schema "
+        f"change (update the pattern) or the version is malformed."
+    )